Mailing giant Pitney Bowes has added another lawsuit to its stack of legal proceedings against Stamps.com, this one claiming that the online company's NetStamps product infringes on several P-B patents.

Launched last July with the blessing of the U.S. Postal Service, the NetStamps app is a form of e-postage that can be printed out and used just like regular stamps.

Stamford-Conn.-based Pitney Bowes , a $4.1 billion company that is an acknowledged leader in the mailing and document management business, said it is seeking to halt what it called the unlicensed use of its intellectual property in the NetStamps application.

The suit was filed in the United States District Court for the District of Delaware. A spokesman for Santa Monica, Calif.-based Stamps.com could not be reached immediately.

Pitney Bowes "is strongly committed to protecting its intellectual property portfolio" said Sara Moss, senior vice president and general counsel at Pitney Bowes.

Stamps.com was sued by Pitney Bowes in 1999 for alleged infringement of patents covering key processes for shipping and tracking packages and mail. Legal action is still pending. Stamps.com in 2001 sued Pitney Bowes, claiming infringement on patents held by Salim Kara, the founder of E-Stamp, which Stamps.com had acquired earlier that year.

The Stamps.com Version 2.5 software lets users print both NetStamps and the company's old form of Internet Postage interchangeably. A new version, 3.0, was just launched. It lets customers print complete shipping labels with postage using only regular 8 1/2 x 11 paper, thus eliminating the need for special labels.

Stamps.com rival E-Stamp Corp. sold its patents and other intellectual property rights as well as the E-Stamp name and E-Stamp.com domain to Stamps.com in April of 2001.